Improvement in fusible safety-plugs



NITED STATES PATENT OFFICE.

F. CURTIS, OF NEWBURYPORT, MASSACHUSETTS,

IMPROVEMENT IN FUSIBLE SAFETY-PLUGS.

Specification forming part of Letters Patent No. 40,677, dated November 24, 1863.

To all whom it may concern:

Be it known that I, F. CURTIS, of N ewburyport, in the county of Essex and State of Massachusetts, have invented a new and useful Improvement in Fusible Safety Plugs for Steam-Boilers and other Apparatus; and I do hereby declare that the following is a full,

clear, and exact description of the same.

The safety-plugs in common use are very unreliable after having been in use for some time. When composed of an alloy the particles of the different metals have a galvanic action which will in time infallibly remove the more fusible metal, and when the water in contact with them is not very pure the metal thus removed is replaced by a stony deposit from the water, and the plug is worse than useless, because it lulls all suspicion of danger, and, moreover, the film of oxide which is formed upon it at first, and is commonly relied on to protect it from further corrosion, is

only proof that destruction has begun. The objection to a plug of lead or any single metal, which has been sometimes used, is that it does not melt at a sufficiently-low temperature for safety in most cases.

The object of my invention is to obviate all these dangers; and to this end it consists in protecting a fusible safety-plug by any known process with a coating of a metal less fusible and less liable to corrode than the metal or alloy of which the body of the plug is composed, but so thin as to offer no appreciable.

resistance to pressure when the metal or alloy of which the body is composed is softened or melted by heat.

The simplest and easiest mode of applying the protecting-coating to the plug is by the galvano-plastic process, and the metalsof which it may be composed are pure copper, silver, gold, and platinum.

I do not confine myself tothe use of any F. CURTIS.

Witnesses GEORGE A. UHOATE, GEo. H. STEVENS. 

